Known in the art is a method for refining and separating a krypton-xenon concentrate comprising the steps of preparing the krypton-xenon concentrate from a weak krypton-xenon mixture, which is pre-purified from hydrocarbons, using a method of low temperature rectification, refining the krypton-xenon concentrate to remove fluorine- and/or chlorine-containing impurities, and subsequently dividing the matter into high-purity krypton and high-purity xenon in a rectifying column. Purification of the krypton-xenon concentrate to remove fluorine- and/or chlorine-containing impurities in the known method is provided through chemical adsorption at a temperature comprised predominately between 450° and 550° C. on a solid adsorbent comprising, for the most part, more than 50% of phyllosilicates. Carbon dioxide and water are thus formed, which are removed by absorption of the carbon dioxide and the water in one of two reversing absorbers using molecular sieves. Oxygen traces are removed by contacting with a copper-nickel catalyst.
The known method has drawbacks with regard to high energy capacity and high specific quantity of metal required due to the use of high temperature processes in cryogenic technology. Further, it is impossible to obtain especially pure krypton and xenon in one column simultaneously.
The closest to the present invention, in terms of technical essence, is an adsorption-rectification method for separating gases with the use of freezing steps, which provides for liberating xenon and krypton from a gas mixture containing krypton, xenon, argon, and nitrogen. According to the known method, xenon is absorbed in a silica gel absorber from a gas flow pre-purified from carbon dioxide and moisture, with the remaining gas mixture directed first to a rectifying column for preliminary krypton separation and then to a krypton column. The xenon fraction is liberated in the process of reactivation of the absorber, and is intermittently directed to a nitrogen-cooled freezing apparatus. In the apparatus, while the xenon and krypton freezes, an appreciable portion of nitrogen with an admixture of krypton is removed from the fraction, and added to the gas flow at the inlet of the column for krypton pre-separation. The xenon concentrate obtained after fusing the cryogenic residual is purified to remove nitrogen/krypton remainders in the xenon column.
The drawbacks of the known method are its discontinuity associated with the use of a freezing apparatus being filled with xenon fractions at regular intervals, additional expenditures of a coolant and electric energy on the alternating freezing and heating of the xenon fractions, as well as the impossibility of obtaining especially pure krypton and xenon, when starting with the presence in a base mixture of, for example, fluorine/chlorine-containing compounds.
Also known is an apparatus for purifying and separating a krypton-xenon concentrate, comprising an outfit-pipeline-connected low-temperature rectifying column for producing a krypton-xenon concentrate, a vessel filled with a solid sorbent containing phyllosilicates, for removing fluorine- and/or chlorine-containing impurities from the concentrate at a temperature of between 450° and 550° C., a pair of reversing absorbers, a reaction vessel with a copper-nickel catalyst, and a rectifying column for the production of high-purity krypton and xenon. The device is disadvantageous in that it has a high energy capacity and a high specific quantity of metal, and because of the impossibility of obtaining in one column simultaneously especially pure krypton and xenon.
Also known is a device for separating gases, comprising two adsorbents filled with molecular sieves, a silica gel adsorbent, a xenon freezing means, a preliminary krypton separation rectifying column, and krypton and xenon rectifying columns connected via pipelines with the outfit. The device is disadvantageous with respect to its discontinuity of operation associated with the use of freezing means intermittently filled with xenon fractions, additional expenditures of a coolant and electric energy in cooling and heating the freezing means as well as the impossibility of obtaining especially pure krypton and xenon, when starting with, for example, fluorine- and/or chlorine-containing impurities in a base mixture.